Signal transmission circuit, battery monitoring device, and battery monitoring method

ABSTRACT

A signal transmission device and a battery monitoring device are provided. The signal transmission device is connected to an operation device including an operation circuit for performing an operation based on a first voltage, a measurement circuit for obtaining measurement data based on the first voltage, and a process control circuit for operating based on a lower voltage and control an operation of the operation circuit based on the measurement data, and transmits and receives signals between the process control circuit and the measurement circuit. The signal transmission device includes a power reception circuit for supplying power from the power transmission circuit to the measurement circuit to acquire measurement data, and a power transmission circuit for transmitting the power from a process control circuit to the power reception circuit to receive the measurement data from the power reception circuit and supply the same to the process control circuit.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japan Application no.2017-117998, filed on Jun. 15, 2017. The entirety of the above-mentionedpatent application is hereby incorporated by reference herein and made apart of this specification.

BACKGROUND Technical Field

The disclosure relates to a signal transmission circuit, a batterymonitoring device, and a battery monitoring method.

Description of Related Art

In a battery device such as an electric vehicle, the entire device iscontrolled while monitoring much information such as voltages andtemperatures of individual battery cells constituting a battery. Forexample, such a battery device includes a control circuit forcontrolling the entire device and a measurement circuit having anoperational amplifier or the like for measuring voltages andtemperatures of individual battery cells. The control circuit performscontrol based on information such as voltages and temperatures measuredby the measurement circuit.

A battery is configured by connecting a large number of battery cells inseries and a potential difference between both ends extends to severalhundred volts. Furthermore, a potential of a terminal connected to eachbattery cell significantly fluctuates according to a change in an amountof electric current or polarity due to acceleration or deceleration ofthe electric vehicle or the like. On the other hand, the control circuitfor controlling the entire device is a digital circuit operating at 5 Vor less. Thus, information such as a voltage and a temperature istransmitted between blocks having a potential difference of severalhundred volts. Signal transmission is performed while maintainingisolation between blocks having a potential difference.

A device using a photocoupler and an isolation transformer has beenproposed as a device configured to perform signal transmission whilemaintaining isolation between blocks having a potential difference (forexample, see Patent Document 1: Japanese Laid-Open No. 2014-135838).

In signal transmission between blocks having a potential difference,transformers, photocouplers, high-voltage-resistant semiconductor parts,and the like are used as in the above-described related art, but theseparts are large and expensive. In a device requiring high reliability, atransmission path is generally duplexed. However, in this case, thenumber of high-voltage-resistant semiconductor parts, the number oftransformers, and the number of photocouplers are doubled, and a size ofthe device becomes larger and the device becomes more expensive.

Also, to measure voltages and temperatures of individual battery cells,a measurement circuit including an operational amplifier and the like isprovided and power is supplied to the measurement circuit. It isconceivable to supply power from the individual battery cells to themeasurement circuit, but it becomes impossible to perform an operationif the battery cell is fully discharged.

Moreover, in industrial devices, office devices, household appliances,or photovoltaic power generation application devices operating with acommercial AC power supply of 100 V or more, the voltage and current ofa high-voltage power line are also measured, and processing and controlin a digital circuit of a low-voltage operation are performed. In thiscase, an issue similar to that described above is also found.

Also, because a control based on ON/OFF timings of transistors andthyristors such as a chopper control is performed in the above-describeddevices, timings of information transmission and reception areimportant, and an increase in an information delivery time and a changein a delay time cannot be tolerated.

Also, high-resistant-voltage semiconductor parts, transformers, andphotocouplers are physically fixed, and positions of a transmission sideand a reception side cannot be changed or rotated. For attachment anddetachment thereof, connectors having contact points are adopted, andconnection reliability becomes an issue. Also, these cannot be immersedin water.

SUMMARY

An embodiment of the invention provides a signal transmission deviceconnected to an operation device including an operation circuitconfigured to perform an operation based on a first voltage from a powersupply, a measurement circuit configured to obtain measurement data bymeasuring an electrical signal using the first voltage as a reference,and a process control circuit configured to operate based on a secondvoltage obtained by converting the first voltage into a voltage with avoltage level less than the first voltage and control an operation ofthe operation circuit based on the measurement data and configured totransmit and receive a signal between the process control circuit andthe measurement circuit, the signal transmission device including: apower transmission circuit having a power-transmission-side resonancecircuit including a power transmission coil and apower-transmission-side resonance capacitor and configured to wirelesslyperform transmission of power and transmission and reception ofinformation according to an alternating current (AC) magnetic field fromthe power transmission coil; and a power reception circuit having apower-reception-side resonance circuit including a power reception coiland a power-reception-side resonance capacitor and configured towirelessly perform reception of power and transmission and reception ofinformation via the power reception coil according to the AC magneticfield, wherein the power reception circuit supplies the power from thepower transmission circuit to the measurement circuit and acquires themeasurement data from the measurement circuit to transmit the acquiredmeasurement data to the power transmission circuit, and wherein thepower transmission circuit transmits the power from the process controlcircuit to the power reception circuit and receives the measurement datafrom the power reception circuit to supply the received measurement datato the process control circuit.

An embodiment of the invention provides a battery monitoring device formonitoring states of n (n is an integer greater than or equal to 2)battery cells, the battery monitoring device including: a powertransmission circuit having m (m is an integer less than or equal to n)power transmission coils and configured to cause any one of the n powertransmission coils to generate an AC magnetic field and wirelesslyperform transmission of power and transmission and reception ofinformation; n power reception circuits provided in correspondence withthe n battery cells and the m power transmission coils, each of the npower reception circuits having a power reception coil and wirelesslyperforming reception of power and transmission and reception ofinformation via the power reception coil; and n measurement circuitsprovided in correspondence with the n power reception circuits and the nbattery cells and configured to receive power supplied from the n powerreception circuits and measure voltage values of the n battery cells,wherein the power transmission circuit selects any one of the In powertransmission coils in accordance with a battery cell of a monitoringtarget among the n battery cells, causes the selected power transmissioncoil to generate the AC magnetic field, and receives a result ofmeasuring a voltage value of the battery cell of the monitoring target.

An embodiment of the invention provides a battery monitoring method foruse in aforesaid battery monitoring device, the battery monitoringmethod comprising the steps of: sequentially selecting, by the powertransmission circuit, each of the n battery cells as a battery cell of amonitoring target, selecting a corresponding power transmission coilamong the m power transmission coils, and causing the power transmissioncoil to generate the AC magnetic field; receiving a measurement resultof a voltage value of the battery cell of the monitoring target from thepower reception circuit; calculating an average value of the measurementresults of the n battery cells; comparing a number of high-voltage cellshaving a voltage which is a predetermined allowable value greater thanthe average value among the n battery cells with a number of low-voltagecells having a low voltage which is the predetermined allowable valueless than the average value; and discharging the high-voltage cells ifthe number of high-voltage cells is greater than the number oflow-voltage cells and charging the low-voltage cells if the number oflow-voltage cells is greater than the number of high-voltage cells.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of an operationdevice including a signal transmission device according to Embodiment 1.

FIG. 2 is a block diagram illustrating a configuration of apower-reception-side circuit.

FIG. 3 is a block diagram illustrating a configuration of apower-transmission-side circuit.

FIG. 4(a) is a plan view and FIG. 4(b) is a cross-sectional perspectiveview (b) of conductor patterns of a power transmission coil and a powerreception coil.

FIG. 5 is a plan view illustrating a positional relationship between theconductor patterns of the power transmission coil and the powerreception coil and the resonance capacitor.

FIG. 6 is a plan view illustrating another example of the conductorpatterns of the power transmission coil and the power reception coil.

FIG. 7(a) and FIG. 7(b) are plan views illustrating another example ofthe conductor patterns of the power transmission coil and the powerreception coil.

FIG. 8 is a block diagram illustrating a configuration of a signaltransmission device according to Embodiment 2.

FIG. 9 is a flowchart illustrating operations of a power transmissioncircuit and a power reception circuit including a timing notificationoperation.

FIG. 10 is a block diagram illustrating a configuration of a batterymonitoring device according to Embodiment 3.

FIG. 11 is a block diagram illustrating details of a power receptionblock including a power-reception-side circuit.

FIG. 12 is a block diagram illustrating another configuration example ofthe battery monitoring device.

FIG. 13 is a flowchart illustrating a battery monitoring operation.

FIG. 14 is a diagram illustrating a circuit example in which thepower-reception-side circuit has a resonance switching circuit.

FIG. 15 is a block diagram illustrating another configuration example ofthe battery monitoring device.

FIG. 16(a) and FIG. 16(b) are diagrams schematically illustrating anantenna structure of the battery monitoring device.

FIG. 17 is a diagram schematically illustrating an antenna structure ofthe battery monitoring device.

FIG. 18(a) and FIG. 18(b) are diagrams illustrating a configurationexample of a power transmission coil.

FIG. 19 is a block diagram illustrating a configuration of the batterymonitoring device in which a capacitor is connected in series to thepower transmission coil.

FIG. 20 is a block diagram illustrating a configuration of the batterymonitoring device in which a capacitor is connected in series to a powerreception coil.

FIG. 21 is a block diagram illustrating a configuration of a batterymonitoring device according to Embodiment 4.

FIG. 22 is a diagram schematically illustrating an antenna structure ofthe battery monitoring device.

FIG. 23 is a diagram schematically illustrating an antenna structure ofthe battery monitoring device.

DESCRIPTION OF THE EMBODIMENTS

The embodiments of the invention provide a signal transmission deviceand a battery monitoring device capable of performing signaltransmission between blocks having a potential difference with ahigh-reliability and small-scale configuration.

According to the signal transmission device of one or some exemplaryembodiments of the invention, signal transmission between blocks havinga potential difference can be performed with a high-reliability andsmall-scale configuration.

Hereinafter, embodiments of the disclosure will be described withreference to the drawings. In the description and the accompanyingdrawings of the following embodiments, substantially the same orequivalent parts are denoted by the same reference signs.

Embodiment 1

FIG. 1 is a block diagram illustrating an overall configuration of adevice including an operation device 100, a power reception circuit 200,and a power transmission circuit 300 according to the presentembodiment. The power reception circuit 200 and the power transmissioncircuit 300 constitute a signal transmission device 400.

The operation device 100 includes a high-voltage circuit 10, atransformer 11, a rectification circuit 12, a low-voltage circuit 13,and a measurement circuit 14.

For example, the high-voltage circuit 10 is a high-voltage operationcircuit configured to operate based on an alternating current (AC)voltage which is a high voltage, such as an electric motor, a heatingdevice, an electric furnace, or a chemical reaction layer. Thehigh-voltage circuit 10 operates based on an AC voltage supplied from anAC power supply ACS. The AC power supply ACS is, for example, a powersupply for transmitting a commercial AC voltage of AC 100 V.

The transformer 11 is provided in parallel with a voltage supply lineconnecting the AC power supply ACS and the high-voltage circuit 10, andconverts a voltage level of the AC voltage transmitted from the AC powersupply ACS, for example, from 100 V to 5 V.

The rectification circuit 12 includes, for example, a diode bridge towhich four rectification diodes are connected and a smoothing capacitor.The rectification circuit 12 performs full-wave rectification andsmoothing of an AC voltage whose voltage level is converted by thetransformer 11 (for example, AC 5 V), and generates a direct current(DC) voltage (for example, DC 5 V). The rectification circuit 12supplies the generated DC voltage to the low-voltage circuit 13.

The low-voltage circuit 13 includes, for example, a digital circuit or aCPU, and controls the high-voltage circuit 10 and the entire device bysupplying a control signal CS. Also, the low-voltage circuit 13 suppliespredetermined power V1 to the power transmission circuit 300. Thelow-voltage circuit 13 performs these operations based on the DC voltagesupplied from the rectification circuit 12.

The measurement circuit 14 measures the voltage of the AC power supplyACS divided by a resistor R1 (for example, 100 kΩ). Also, themeasurement circuit 14 measures an AC according to a voltage across aresistor R2 (for example, 1Ω) connected to the AC power source ACS. Themeasurement circuit 14 converts measured voltage and current valuesaccording to AD conversion, extracts the converted values as data, andsupplies the data as measurement data Md to the power-reception-sidecircuit 20.

The power reception circuit 200 includes a power reception coil RC and apower-reception-side circuit 20. The power transmission circuit 300includes a power transmission coil TC and a power-transmission-sidecircuit 30.

FIG. 2 is a block diagram illustrating a configuration of the powerreception circuit 200.

The power reception coil RC configures a resonance circuit 21 togetherwith a resonance capacitor C1. The power reception coil RC and theresonance capacitor C1 are magnetically coupled to an AC magnetic fieldof a high frequency (for example, 13.56 MHz) generated by the powertransmission coil TC of the power transmission circuit 300, generate anAC voltage (a high-frequency signal) corresponding to the AC magneticfield, and apply the generated AC voltage to lines L1 and L2. Althoughthe resonance circuit 21 is configured as a parallel resonance circuitin which the power reception coil RC and the resonance capacitor C1 areconnected in parallel, the resonance circuit 21 may be a seriesresonance circuit or a combination of a parallel resonance circuit and aseries resonance circuit.

The rectification circuit 22 includes a diode bridge to which fourrectification diodes D1 to D4 are connected and a smoothing capacitorSC. The rectification circuit 22 performs full-wave rectification andsmoothing of the AC voltage (high-frequency power) of the lines L1 andL2, converts the AC voltage into a DC voltage, applies the DC voltage tolines L5 and L6, and supplies the DC voltage to a power supply and biascircuit 23.

The power supply and bias circuit 23 includes a power-supply circuit 24configured to supply a power-supply voltage to a communication circuit26 and a control circuit 27 and a bias circuit 25 configured to supply abias voltage and a bias current to the communication circuit 26 and thecontrol circuit 27.

The communication circuit 26 operates based on the power-supply voltagefrom the power-supply circuit 24 and the bias voltage and the biascurrent from the bias circuit 25, and uses the high-frequency signalfrom the power reception coil RC as a clock to perform bidirectionalcommunication based on amplitude shift keying (ASK) modulation. Thecommunication circuit 26 performs bidirectional communication with thepower-transmission-side circuit 30 via the power reception coil RC.

The control circuit 27 operates based on the power-supply voltage fromthe power-supply circuit 24 and the bias voltage and the bias currentfrom the bias circuit 25 and controls the operation of the entirepower-reception-side circuit 20 by exchanging data and the clock withthe communication circuit 26.

FIG. 3 is a block diagram illustrating a configuration of the powertransmission circuit 300.

An AC signal source 31 includes a quartz oscillation circuit or thelike, generates an AC signal of 13.56 MHz, and supplies the generated ACsignal to a driving circuit 32.

The driving circuit 32 amplifies power of the AC signal supplied fromthe AC signal source 31 to generate a driving current and transmits thegenerated driving current to lines L3 and L4. Thereby, a high-frequencycurrent flows through the power transmission coil TC.

The control circuit 33 exchanges data and a clock with the communicationcircuit 34 and controls the operation of the entirepower-transmission-side circuit 30.

The communication circuit 34 performs bidirectional communication basedon ASK modulation via the power transmission coil TC. Also, thecommunication circuit 34 may perform communication using a near fieldcommunication (NFC) communication method or the like.

The power transmission coil TC forms a resonance circuit 35 togetherwith a resonance capacitor C2. The power transmission coil TC and theresonance capacitor C2 generate an AC magnetic field based on a drivingcurrent supplied from the driving circuit 32. Also, although theresonance circuit 35 is configured as a parallel resonance circuit inwhich the power transmission coil TC and the resonance capacitor C2 areconnected in parallel, the resonance circuit 35 may be a seriesresonance circuit or a combination of a parallel resonance circuit and aseries resonance circuit.

In communication based on magnetic-field coupling of the powertransmission coil TC and the power reception coil RC, for example, ASKmodulation with a modulation index of about 10% is used. Thereby,communication can be performed while power is supplied.

Next, the operation of the signal transmission device 400 of the presentembodiment will be described with reference to FIG. 1 again.

First, when the operation device 100 is activated, the low-voltagecircuit 13 starts an operation based on a DC voltage of 5 V obtained byconverting an AC voltage of AC 100 V from the AC power supply ACS in thetransformer 11 and the rectification circuit 12. The low-voltage circuit13 supplies a control signal CS to cause the high-voltage circuit 10 tobe operated. Thereby, the operation device 100 starts an operation.Also, the low-voltage circuit 13 supplies power V1 to thepower-transmission-side circuit 30 of the power transmission circuit300.

The power-transmission-side circuit 30 receives the power V1 from thelow-voltage circuit 13 and applies a high-frequency power of 13.56 MHzto the power transmission coil TC to generate a high-frequency ACmagnetic field (hereinafter referred to as a high-frequency magneticfield). The power transmission coil TC and the power reception coil RCare magnetic-field coupled according to the generated high-frequencymagnetic field and generate high-frequency power according toelectromagnetic induction. The power-reception-side circuit 20 issupplied with high-frequency power and a clock of 13.56 MHz via thepower reception coil RC.

The power-reception-side circuit 20 supplies a part of thehigh-frequency power obtained via the power reception coil RC as powerV2 to the measurement circuit 14. The measurement circuit 14 measures avoltage and a current of the AC power supply ACS and performs ADconversion to generate measurement data Md. The measurement circuit 14supplies the measurement data Md to the power-reception-side circuit 20.

The power-reception-side circuit 20 transmits the measurement data Md tothe power transmission circuit 300 via the power reception coil RC. Thepower-transmission-side circuit 30 of the power transmission circuit 300receives the measurement data Md via the power transmission coil TC.

The power-transmission-side circuit 30 supplies the measurement data Mdto the low-voltage circuit 13. The low-voltage circuit 13 makes varioustypes of determinations based on the measurement data Md and controlsthe high-voltage circuit 10.

As described above, in the signal transmission device 400 of the presentembodiment, the exchange of the measurement data Md and the power supplyto the measurement circuit 14 are performed using the high-frequencymagnetic field of 13.56 MHz according to the magnetic-field couplingbetween the power transmission coil TC and the power reception coil RC.

According to the signal transmission device 400 of the presentembodiment, signal transmission can be performed according to themagnetic-field coupling between the power transmission coil TC and thepower reception coil RC, so that electrical isolation can be easilyimplemented. Therefore, it is possible not to use expensive andlarge-size parts such as a photocoupler or a transformer.

Also, because it is possible to supply power to the measurement circuit14 according to the magnetic-field coupling between the powertransmission coil TC and the power reception coil RC, a sensor circuit,an operational amplifier circuit for signal processing, an AD convertercircuit, and a digital circuit for arithmetic processing can be arrangedas the measurement circuit 14. Accordingly, it is possible to implementa high-performance and high-efficiency device capable of performingadvanced measurement and data processing, compression of communicationdata, and the like.

Also, the power transmission coil TC and the power reception coil RC canbe shielded from the outside world by a magnetic sheet or the like, andit is possible to easily prevent external interference and informationleakage.

Also, because the power transmission coil TC and the power receptioncoil RC are detachable and can be operated while they mutually rotate ortheir positions change, it is possible to eliminate electrical contactpoints and create inexpensive and highly reliable signal connectionpoints.

Also, because the power transmission coil TC and the power receptioncoil RC can be operated even in a state in which they are immersed inwater, they can also be used for exchanging measurement data in the seaor underwater.

Also, power supply to the measurement circuit 14 or the like accordingto the magnetic field may be simultaneously performed in parallel withthe communication operation according to magnetic-field coupling or maybe performed according to a non-modulated high-frequency magnetic fieldin which no communication is performed.

Next, the configurations of the power transmission coil TC and the powerreception coil RC will be described with reference to FIGS. 4(a) and4(b).

The power transmission coil TC and the power reception coil RC areformed by forming a conductor pattern of the power transmission coil ina first wiring layer from the first wiring layer and a second wiringlayer provided on both surfaces of a substrate of an isolation material(for example, a substrate material FR-4 with a thickness of 1.6 mm),forming a conductor pattern of the power reception coil in the secondwiring layer, and providing wiring in a via connected between the firstwiring layer and the second wiring layer.

FIG. 4(a) is a plan view when the conductor pattern of the powertransmission coil TC is viewed from the first wiring layer side of thesubstrate in a top view and is a plan view when the conductor pattern ofthe power reception coil RC is viewed from the second wiring layer sideof the substrate in a top view. FIG. 4(b) is a cross-sectionalperspective view of the power transmission coil TC and the powerreception coil RC in a broken line part of FIG. 4(a).

The power transmission coil TC and the power reception coil RC haveconductor patterns in which conductor wires made of copper foil, forexample, having a thickness of 35 m, are formed in a spiral shape of twoor more turns (more than one turn). An end of the conductor pattern ofthe power transmission coil TC is connected to thepower-transmission-side circuit 30. An end of the conductor pattern ofthe power reception coil RC is connected to the power-reception-sidecircuit 20.

As illustrated in FIG. 4(a), the power transmission coil TC has a wiringpart WP1 including a continuous conductor wire having one end connectedto a resonance capacitor C2 (not illustrated) constituting a resonancecircuit, and a spiral part SP1 including a continuous conductor wire ofa spiral shape having a first end connected to the resonance capacitorC2. The spiral part SP1 has a conductor wire part that crosses a spacebetween a second end of the spiral part SP1 and the other end of thewiring part WP1 (indicated by a mark x in FIG. 4(a)).

Also, the power transmission coil TC has a connection part configured toconnect the second end of the spiral part SP1 and the other end of thewiring part WP1. The connection part includes a continuous conductorwire part CP1 provided in the second wiring layer and a via wiring partVP passing through a pair of vias provided between the first wiringlayer and the second wiring layer. That is, a crossing of wiring of thepower transmission coil TC is implemented by the conductor wire part CP1and the via wiring part VP.

The power reception coil RC has a wiring part WP2 including a continuousconductor wire having one end connected to a resonance capacitor C1 (notillustrated) constituting a resonance circuit and a spiral part SP2including a continuous conductor wire of a spiral shape having a firstend connected to the resonance capacitor C1. The spiral part SP2 has aconductor wire part that crosses a space between the second end of thespiral part SP2 and the other end of the wiring part WP2 (indicated by amark x in FIG. 4(a)).

Also, the power reception coil RC has a connection part configured toconnect the second end of the spiral part SP2 and the other end of thewiring part WP2. The connection part includes a continuous conductorwire part CP2 provided in the first wiring layer as illustrated in FIG.4(a) and a via wiring part VP passing through a pair of vias providedbetween the first wiring layer and the second wiring layer asillustrated in FIG. 4(b). That is, a crossing of wiring of the powerreception coil RC is implemented by the conductor wire part CP2 and thevia wiring part VP.

The conductor wire part CP1 of the connection part of the powertransmission coil TC is provided at a position (i.e., an isolatedposition) separated from the spiral part SP2 of the power reception coilRC in the second wiring layer. Likewise, the conductor wire part CP2 ofthe connection part of the power reception coil RC is provided at aposition (i.e., an isolated position) separated from the spiral part SP1of the power transmission coil TC in the first wiring layer.

Also, the conductor wire part CP1 of the connection part of the powertransmission coil TC is arranged inside an inner diameter of the spiralpart SP2 of the power reception coil RC in the second wiring layer. Theconductor wire part CP2 of the connection part of the power receptioncoil RC is arranged inside an inner diameter of the spiral part SP1 ofthe power transmission coil TC in the first wiring layer.

The spiral part SP1 of the power transmission coil TC and the spiralpart SP2 of the power reception coil RC are arranged so that theyoverlap via the first wiring layer, the substrate, and the second wiringlayer, except for a part where the conductor wire part CP1 and theconductor wire part CP2 are positioned.

The power transmission coil TC and the power reception coil RC are coilsconfigured to handle a high-frequency magnetic field of 13.56 MHz andhave an inductance of about 0.5 to 1 microhenry, for example. This isbecause the reactance of the coil is about 42.6 to 85.2Ω, which issuitable for handling the reactance at a power-supply voltage of about 5V frequently used in electronic devices. On the other hand, an outerdiameter size of the coil is, for example, about 20 mm due to thecircumstances of a device size. In order to satisfy these conditions, acoil is formed in a spiral shape of two or more turns (the number ofturns which is greater than one), and the coil has a crossing withisolation.

In the power transmission coil TC and the power reception coil RCaccording to the present embodiment, a crossing is implemented withisolation according to the conductor wire parts (CP1 and CP2) providedin the wiring layer opposite to the spiral parts (SP1 and SP2) and thevia wiring parts (VP) provided in the pair of vias. According to thisconfiguration, it is possible to implement a crossing with isolation inan inexpensive two-layer printed substrate without using a substrate ofa large number of layers such as four layers.

Also, although slight disturbance occurs in a region where each coilcrosses over (hereinafter referred to as a crossing region), aninfluence on operations and characteristics is sufficiently small due toa slight change in self-inductance of each coil and a coefficient ofcoupling between the two coils.

Also, it is possible to secure amounts of isolation resistance of thepower transmission coil TC and the power reception coil RC by setting athickness of an isolation substrate sandwiched between front and rearconductors, a distance in a planar direction between the conductorpattern (the spiral part SP1 and the wiring part WP1) of the powertransmission coil TC in the first wiring layer and the conductor pattern(the conductor wire part CP2) of the power reception coil RC, and adistance in a planar direction between the conductor pattern (the spiralpart SP2 and the wiring part WP2) of the power reception coil RC in thesecond wiring layer and the conductor pattern (the conductor wire partCP1) of the power transmission coil TC to safe sizes. At this time, itis possible to widen an interval between the conductor pattern of thepower transmission coil TC and the conductor pattern of the powerreception coil RC of each layer in accordance with a desired isolationdistance.

Also, because crossing regions (the conductor wire parts CP2 and CP1)are provided inside the inner diameters of the spiral parts (SP1 andSP2), a compact device can be implemented without increasing an occupiedarea.

FIG. 5 is a plan view illustrating a positional relationship between theconductor patterns of the power transmission coil TC and the powerreception coil RC and the resonance capacitors C1 and C2.

On a connection line (a straight line part in which the wiring part WP1and the spiral part SP1 run in parallel in FIG. 5) associated with theresonance capacitor C2 of the wiring part WP1 and the spiral part SP1,land patterns C2 a and C2 b for making a soldering connection of theresonance capacitor C2 are provided. The land patterns C2 a and C2 b areprovided at intervals within three times the wiring interval of the coilpart of the power transmission coil TC.

Likewise, on a connection line (a straight line part in which the wiringpart WP2 and the spiral part SP2 run in parallel in FIG. 5) associatedwith the resonance capacitor C1 of the wiring part WP2 and the spiralpart SP2, land patterns C1 a and C1 b for making a soldering connectionof the resonance capacitors C1 are provided. The land patterns C1 a andC1 b are provided at intervals within three times the wiring interval ofthe coil part of the power reception coil RC.

As an interlayer length of the conductor pattern of the powertransmission coil TC and the power reception coil RC increases, thenumber of magnetic flux lines interlinked with each other can increaseand the coupling coefficient can increase. In a path between each coiland each resonance capacitor, a large current flows during resonance. Byarranging the capacitor at a near position, it is possible to reduce thenumber of self-interlink magnetic flux lines and prevent the couplingcoefficient from decreasing.

Also, unlike the above, as illustrated in FIG. 6, one of the crossingregions may be arranged inside an inner diameter of the coil (that is,inside the spiral part) and the other may be arranged outside an outerdiameter of the coil (that is, outside the spiral part). For example,when it is necessary to increase a distance in a planar direction forsecuring isolation on either side of a printed substrate, the crossingregion is arranged outside the outer diameter of the coil, so that it ispossible to minimize an increase in an occupied area while increasingthe isolation distance compared with the case where the crossing regionis arranged inside the inner diameter of the coil.

Also, as illustrated in FIGS. 7(a) and 7(b), both the crossing regionsmay be arranged on an outer side of an outer diameter of the coil. Whenit is necessary to increase the distance in the planar direction forsecuring isolation on both sides of the printed substrate, the crossingregion is arranged outside the outer diameter of the coil, so that it ispossible to minimize an increase in an occupied area while increasingthe isolation distance compared with the case where the crossing regionis arranged inside the inner diameter of the coil.

Also, the power reception coil RC may be formed in the first wiringlayer and the power transmission coil TC may be formed in the secondwiring layer.

Although an example in which the power transmission coil TC and thepower reception coil RC have rectangular shapes is illustrated in FIGS.4(a) and 4(b) and FIGS. 5, 6, 7(a), and 7(b), a bent part may be a curveor a square, a circle, an ellipse, a polygon or the like.

Also, although a conductor layer is formed of two layers of the firstwiring layer and the second wiring layer, a plurality of conductorlayers of a multilayer substrate having two or more layers may be used.For example, it is possible to isolate the surface of each coil by usingtwo middle wiring layers from four conductor layers as wiring layers.

Embodiment 2

FIG. 8 is a block diagram illustrating a configuration of a signaltransmission device 410 of the present embodiment. The signaltransmission device 410 is different from the signal transmission device400 of the first embodiment in that a power reception circuit 210 has aclamp circuit 28 and a power transmission circuit 310 has a currentmeasurement circuit 36.

The clamp circuit 28 is provided on an output side of a rectificationcircuit 22 between lines L5 and L6. The clamp circuit 28 includes aZener diode and a connection switch. The clamp circuit 28 switches astate of the connection switch to an ON or OFF state in accordance withthe supply of a load switching signal LS from a control circuit 27.Thereby, the load state of the rectification circuit 22 changes and thestate of the high-frequency magnetic field changes. That is, the clampcircuit 28 is a load switching circuit configured to switch the loadstate in accordance with the load switching signal.

The current measurement circuit 36 is provided in a driving circuit 32.The current measurement circuit 36 detects a change in a high-frequencymagnetic field based on currents flowing through lines L3 and L4 andnotifies a control circuit 33 of a detection result.

According to operations of the clamp circuit 28 and the currentmeasurement circuit 36, it is possible to provide a notification fromthe power reception circuit 210 to the power transmission circuit 310.Operations of the power transmission circuit and the power receptioncircuit including a timing notification operation will be described withreference to the flowchart of FIG. 9.

First, the power transmission circuit 310 is activated to cause a powertransmission coil TC to generate a high-frequency magnetic field (stepS101). The power transmission circuit 310 supplies power and a clock tothe power reception circuit 210. The power reception circuit 210 isactivated in accordance with power supply and clock supply (step S201).

The power transmission circuit 310 and the power reception circuit 210transmit and receive a communication message according to bidirectionalcommunication via magnetic-field coupling between the power transmissioncoil TC and a power reception coil RC. The power transmission circuit310 continues power supply and clock supply in parallel with thetransmission and reception of the communication message. Each of thepower transmission circuit 310 and the power reception circuit 210performs initial setting based on setting information obtained accordingto the transmission and reception of the communication message andperforms normality diagnosis to diagnose whether or not the operation isperformed normally (steps S102 and S202).

The control circuit 27 of the power reception circuit 210 determineswhether or not a high-frequency magnetic field is in a steady state(step S203). If it is determined that the high-frequency magnetic fieldis not in the steady state (step S203: No), the process proceeds to stepS210 and the operation is stopped.

On the other hand, when it is determined that the high-frequencymagnetic field is in the steady state (step S203: Yes), the controlcircuit 27 determines whether or not a timing notification is necessary(step S204).

When it is determined that the timing notification is necessary (stepS204: Yes), the control circuit 27 controls the clamp circuit 28 toperform switching between ON and OFF states (step S205). Thereby, thehigh-frequency magnetic field changes.

The control circuit 33 of the power transmission circuit 310 determineswhether or not the high-frequency magnetic field is in the steady state(step S103). If it is determined that the high-frequency magnetic fieldis not in the steady state (step S103: No), the process proceeds to stepS109 and the high-frequency magnetic field and the operation of thedevice are stopped.

On the other hand, when it is determined that the high-frequencymagnetic field is in the steady state (step S103: Yes), the currentmeasurement circuit 36 detects a change in a current due to a change inthe high-frequency magnetic field and notifies the control circuit 33 ofa detection result (step S104).

The control circuit 33 of the power transmission circuit 310 determineswhether or not information exchange (communication) with the powerreception circuit 210 is necessary (step S105). Likewise, the controlcircuit 27 of the power reception circuit 210 determines whether or notinformation exchange (communication) with the power transmission circuit310 is necessary (step S206).

When it is determined that information exchange with the power receptioncircuit 210 is necessary (steps S105 and S206: Yes), the powertransmission circuit 310 and the power reception circuit 210 perform acommunication operation according to magnetic-field coupling between thepower transmission coil TC and the power reception coil RC, and exchangeinformation including a communication message with the power receptioncircuit 210 (steps S106 and S207). The power transmission circuit 310supplies power and a clock to the power reception circuit 210 inparallel with the communication operation.

When it is determined that information exchange with the powertransmission circuit 310 is unnecessary (step S206: No), the powerreception circuit 210 performs a standby operation (step S208). When itis determined that information exchange with the power reception circuit210 is unnecessary (step S105: No), the power transmission circuit 310continuously generates the high-frequency magnetic field from the powertransmission coil TC (step S107).

The control circuit 33 of the power transmission circuit 310 determineswhether or not to continue the power supply and clock supply operationbased on the high-frequency magnetic field (step S108). Likewise, thecontrol circuit 27 of the power reception circuit 210 determines whetheror not to continue the standby operation for receiving the power supplyand the clock supply (step S209).

When it is determined that the power supply and clock supply operationbased on the high-frequency magnetic field will be continued (step S108:Yes), the control circuit 33 of the power transmission circuit 310returns to step S103 and determines whether or not the high-frequencymagnetic field is in the steady state again. Likewise, when it isdetermined that the standby operation for receiving the power supply andthe clock supply will be continued (step S209: Yes), the control circuit27 of the power reception circuit 210 returns to step S203 anddetermines whether or not the high-frequency magnetic field is in thesteady state again.

When it is determined that the power supply and clock supply operationbased on the high-frequency magnetic field will not be continued (stepS108: No), the power transmission circuit 310 stops the high-frequencymagnetic field and stops the operation (step S109). When it isdetermined that the standby operation for receiving the power supply andthe clock supply will not be continued (step S209: No), the powerreception circuit 210 stops the operation (step S210).

A notification is provided from the power reception circuit 210 to thepower transmission circuit 310 at any timing according to the aboveoperation.

In the signal transmission device 410 of the present embodiment,according to the operations of the clamp circuit 28 and the currentmeasurement circuit 36, a notification can be provided from the powerreception circuit 210 to the power transmission circuit 310 at anytiming in addition to communication based on the magnetic-field couplingbetween the power transmission coil TC and the power reception coil RC.At this time, by securing a voltage of the clamp circuit 28 at a voltage(for example, 3 V) at which the power supply and bias circuit 23 canoperate, it is possible to perform a communication operation using thepower transmission coil TC and the power reception coil RC in parallelwhile providing the notification from the power reception circuit 210 tothe power transmission circuit 310.

For example, the signal transmission device of the present embodiment isparticularly effective when accuracy in time is required for a gatecontrol timing of a transistor or a thyristor of the high-voltagecircuit 10.

Embodiment 3

FIG. 10 is a block diagram illustrating a configuration of a batterymonitoring device 500 of this embodiment. The battery monitoring device500 is provided in a device powered by a battery, for example, such asan electric car or the like, and is a device configured to monitorstates of charge of four battery cells 72 a to 72 d (hereinafter alsocollectively referred to as a battery cell group) connected in series.

A power-reception-side circuit 71 a is connected to the battery cell 72a. A power reception coil RC1 is connected to the power-reception-sidecircuit 71 a. The power reception coil RC1, the power-reception-sidecircuit 71 a, and the battery cell 72 a constitute a power receptioncircuit 700 a. Likewise, power reception circuits 700 b to 700 d areconfigured by providing corresponding power-reception-side circuits (71b to 71 d) and power reception coils (RC2 to RC4) in the battery cells72 b to 72 d. When a configuration common to the power receptioncircuits 700 a to 700 d is described in the following description, theseare also referred to as a power reception circuit 700.

FIG. 11 is a block diagram illustrating details of the power receptioncircuit 700 a including the power-reception-side circuit 71 a. Betweenthe power-reception-side circuit 71 a and the battery cell 72 a, ameasurement circuit 73 for measuring a voltage value and temperature ofthe battery cell 72 a is provided. Also, the power reception circuits700 b to 700 d also have similar configurations.

The measurement circuit 73 measures a voltage of the battery cell 72 athrough an operation of dividing the voltage by a resistor R3. Also, themeasurement circuit 73 measures the temperature of the battery cell 72 athrough a thermistor T1. Also, the measurement circuit 73 has a switchSW0 and a resistor R4 for forcibly discharging the battery cell 72 a,and discharges the battery cell 72 a by turning on the switch SW0 inaccordance with control of the power-reception-side circuit 71 a.

The power-reception-side circuit 71 a includes a power-supply circuit74, a communication circuit 75, a memory 76, an analog to digitalconverter (ADC) 77, and a control circuit 78.

The power-supply circuit 74 supplies a power-supply voltage to each partof the power-reception-side circuit 71 a based on power suppliedaccording to magnetic-field coupling between a power transmission coilTC1 and a power reception coil RC1.

The communication circuit 75 transmits and receives information based onASK modulation via the power reception coil RC1. For example, thecommunication circuit 75 transmits monitoring data obtained by themeasurement circuit 73 to a power-transmission-side circuit 61 via thepower reception coil RC1.

The memory 76 is a nonvolatile memory and stores serial numbers, historyinformation, or the like of the battery cells 72 a in addition tocontrol information (for example, an ID of NFC communication) forcommunication and address information.

The ADC 77 converts the voltage value and the temperature measured bythe measurement circuit 73 according to AD conversion to generatemonitoring data.

The control circuit 78 controls each part of the power-reception-sidecircuit 71 a. Also, the control circuit 78 controls forced dischargingof the battery cell via the resistor R4 and the switch SW0.

Referring again to FIG. 10, the battery monitoring device 500 has apower transmission circuit 600 and power transmission coils TC1 to TC4connected thereto. The power transmission coils TC1 to TC4 are providedat positions corresponding to the power reception coils RC1 to RC4 (thatis, positions at which magnetic-field coupling is performed).

The power transmission circuit 600 has the power-transmission-sidecircuit 61 and switches SW1 to SW8.

The power-transmission-side circuit 61 controls ON/OFF of the switchesSW1 to SW8 to select any one of the four power transmission coils TC1 toTC4, transmits a high-frequency signal of 13.56 MHz, and causes theselected power transmission coil to generate a high-frequency magneticfield. A high-frequency electromotive force is generated byelectromagnetic induction in the power reception coil (any one of RC1 toRC4) coupled to the selected power transmission coil.

The power-transmission-side circuit 61 supplies power and a clock to thepower-reception-side circuit (any one of 71 a to 71 d) connected to thepower reception coil where the high-frequency electromotive force isgenerated to operate the power-reception-side circuit, and transmits andreceives the control information and monitoring data according to abidirectional communication function. The power-transmission-sidecircuit 61 receives a digital signal input/output (indicated as adigital I/O in FIG. 11) from a host control device (not illustrated) andperforms an operation.

FIG. 12 is a block diagram illustrating another configuration example ofthe battery monitoring device of the present embodiment. A power-supplyline from the power-supply circuit 74 of the power-reception-sidecircuit 71 a is connected to the battery cell 72 a via a switch SW9. Theswitch SW9 is switched between ON and OFF by the control circuit 78.

The control circuit 78 controls the switch SW9 so that the switch SW9 isturned on and sets the voltage and current of the power-supply circuit74. Thereby, the power-reception-side circuit 71 a can charge thebattery cell with power obtained from the high-frequency magnetic field.

As illustrated in FIG. 10, if a plurality of battery cells are connectedin series, it is necessary to align the state of charge of each batterycell. Conventionally, when it is determined that the state of chargevaries according to voltage measurement, the state of charge is alignedby causing a cell with a high voltage to be forcibly discharged. Thus,for example, if only the voltage of one battery cell is low, all otherbattery cells must be discharged, consumption of energy is caused and anextra time is required for a related countermeasure.

However, according to this configuration, it is possible to additionallycharge a cell with a low voltage. Accordingly, it is possible to align astate of charge of each battery cell without wasting energy or a time bydischarging cells having a high voltage when the number of cells havingthe high voltage is small and charging cells having a low voltage whenthe number of cells having the low voltage is small in accordance with astate of voltage variation.

In the battery monitoring device having such a configuration, thepower-transmission-side circuit 61 sequentially selects the four powertransmission coils TC1 to TC4 by performing switching between ON and OFFof the switches SW1 to SW8 and performs a battery monitoring operationby sequentially activating and operating the power-reception-sidecircuits 71 a to 71 d corresponding thereto to exchange information.Such a battery monitoring operation will be described with reference tothe flowchart of FIG. 13.

First, the battery monitoring device 500 is activated to perform initialsetting of the device (step S301).

Next, the power-transmission-side circuit 61 selects and connects thepower transmission coil TC1 by turning on the switches SW1 and SW2 andturning off the other switches SW3 to SW8 and causes the powertransmission coil TC1 to generate a high-frequency magnetic field.

The power-transmission-side circuit 61 supplies power and a clock to thepower reception circuit 700 a via the power transmission coil TC1 andthe power reception coil RC1 is magnetic-field coupled with the powertransmission coil TC1. In the power reception circuit 700 a, the voltageand temperature of the battery cell 72 a are measured, and monitoringdata is acquired. The power-reception-side circuit 71 a transmits themonitoring data to the power-transmission-side circuit 61 together withan ID of NFC communication or other information. Thepower-transmission-side circuit 61 receives and inputs informationincluding the monitoring data and causes the information to be stored ina memory (not illustrated) or the like (step S302).

The power-transmission-side circuit 61 selects and connects the powertransmission coil TC2 by turning on the switches SW3 and SW4 and turningoff the other switches SW1 and SW2 and SW5 to SW8 and causes the powertransmission coil TC2 to generate a high-frequency magnetic field. As inthe step S302, the power-transmission-side circuit 61 causes the powerreception circuit 700 b to be operated by supplying the power and theclock, receives the monitoring data including the information of thevoltage and the temperature, and the other information related to thebattery cell 72 b and causes the monitoring data and the otherinformation to be stored in the memory or the like (step S303).

The power-transmission-side circuit 61 selects and connects the powertransmission coil TC3 by turning on the switches SW5 and SW6 and turningoff the other switches SW1 to SW4, SW7 and SW8 and causes the powertransmission coil TC3 to generate a high-frequency magnetic field. As insteps S301 and S302, the power-transmission-side circuit 61 causes thepower reception circuit 700 c to be operated by supplying power and aclock, receives monitoring data including information of a voltage andtemperature and other information related to the battery cell 72 c, andcauses the monitoring data and the other information to be stored in thememory or the like (step S304).

The power-transmission-side circuit 61 selects and connects the powertransmission coil TC4 by turning on the switches SW7 and SW8 and turningoff the other switches SW1 to SW6 and causes the power transmission coilTC4 to generate a high-frequency magnetic field. As in steps S301, S302and S303, the power-transmission-side circuit 61 causes the powerreception circuit 700 d to be operated by supplying power and a clock,receives monitoring data including information of a voltage andtemperature and other information related to the battery cell 72 d, andcauses the monitoring data and the other information to be stored in amemory or the like (step S305).

The power-transmission-side circuit 61 determines whether or not thebattery cells 72 a to 72 d are normal (that is, whether there is noabnormality) based on the acquired monitoring data (step S306). When itis determined that the battery cells 72 a to 72 d are not normal (thatis, there is an abnormality) (step S306: No), thepower-transmission-side circuit 61 reports the information of theabnormal battery cell to a host control device (not illustrated) (stepS307) and proceeds to step S314.

On the other hand, when it is determined that the battery cells 72 a to72 d are normal (that is, there is no abnormality) (step S306: Yes), thepower-transmission-side circuit 61 calculates an average value of thevoltages of the battery cells 72 a to 72 d based on the monitoring data.The power-transmission-side circuit 61 compares the voltage of each ofthe battery cells 72 a to 72 d with the average value, sets the numberof high-voltage cells having high voltages which are a predeterminedallowable width greater than the average value to M, and sets the numberof low-voltage cells having low voltages which are the predeterminedallowable width less than the average value to N (step S308).

The power-transmission-side circuit 61 determines whether M and N areboth zero (that is, whether or not a difference between the voltagevalue of any battery cell and the average value falls within anallowable width) (S309). When it is determined that M and N are bothzero (step S309: Yes), the process proceeds to step S314.

On the other hand, if it is determined that either one of M and N is notzero (step S309: No), the power-transmission-side circuit 61 determineswhether or not N is less than M, i.e., determines whether or not thenumber of cells having low voltages which are the predeterminedallowable width less than the average value is less than the number ofcells having high voltages which are the predetermined allowable widthgreater than the average value (step S310).

When it is determined that N is greater than or equal to M (N is notless than M) (step S310: No), the power-transmission-side circuit 61transmits a discharging instruction for issuing an instruction of forceddischarging of M battery cells having a high voltage which is apredetermined allowable width greater than the average value via powertransmission coils corresponding to the battery cells. Thepower-reception-side circuit connected to a battery cell which is atarget to be forcibly discharged connects the resistor R4 to the batterycell by turning on the switch SW0 and forcibly discharges the batterycell (step S311).

On the other hand, if it is determined that N is less than M (step S310:Yes), the power-transmission-side circuit 61 causes power transmissioncoils corresponding to N battery cells having a low voltage which is thepredetermined allowable width less than the average value to generatehigh-frequency magnetic fields and supplies power to power receptioncoils corresponding to the power transmission coils. Thepower-reception-side circuit charges the battery cell based on thesupplied power (step S312).

The power-transmission-side circuit 61 determines whether or not tocontinue a battery monitoring operation (step S313). When it isdetermined that the battery monitoring operation will be continued (stepS313: Yes), the power-transmission-side circuit 61 returns to step S302and executes the monitoring operation of steps S302 to S305 again.

When it is determined that the battery monitoring operation will not becontinued (step S313: No), the power-transmission-side circuit 61 causesthe generation of the high-frequency magnetic field to be stopped andcauses the operation of the battery monitoring device 500 to be stopped.

According to the above operations, battery monitoring and forceddischarging of the battery cell group are performed while a targetbattery cell is switched according to switching of the switch.

According to the battery monitoring device 500 of the presentembodiment, information of a plurality of battery cells having apotential difference from one another can be exchanged between thepower-reception-side circuit connected to the plurality of battery cellsand the power-transmission-side circuit having a potential differenttherefrom (for example, a vehicle body potential of a vehicle in thecase of an electric vehicle). Although the potential of the battery cellsignificantly changes according to charging and discharging, it ispossible to stably exchange information.

Also, because the power transmission circuit 600 and the power receptioncircuit 700 are electrically isolated, there is no leak current from anybattery cell and no energy is wasted.

Also, because the power transmission coil and the power reception coilare arranged close to each other and some deviation and contaminationare allowed, there is superiority in connection reliability andcost-effectiveness as compared with the case where an electrical contactpoint is provided.

Also, because it is possible to detect a state in which the powertransmission coil and the power reception coil are disconnected fromeach other by measuring a high-frequency current of the powertransmission coil, the connection reliability is high. Also, because ahigh-frequency magnetic field is used, there is no restriction onpolarity and a direction.

Also, a range of the high-frequency magnetic field stays in thevicinity, and external malicious operation access and informationleakage can be prevented. Also, prevention of information leakage andthe like can be further strengthened by shielding with a magnetic sheet.

Also, because power is supplied to the power-reception-side circuitthrough a high-frequency magnetic field, an operation can be performedeven if the battery cell is completely discharged.

By connecting an antenna coil of an NFC reader/writer to the powerreception coil in a state in which the power reception circuit 700 isdisconnected from the power transmission circuit 600, it is possible toactivate and operate the power-reception-side circuit to read and writeinformation in the nonvolatile memory and observe and control thebattery cell. Thereby, a battery pack including the power receptioncircuit 700 can be used as a single NFC tag.

Also, by turning off all the switches SW1 to SW8 in thepower-transmission-side circuit 61, it is possible to disconnect all thepower transmission coils (TC1 to TC4). Accordingly, even when the powertransmission coil and the power reception coil are disposed at positionswhere they can be coupled to each other, it is possible to access thebattery cell from the power transmission coil of another reader/writer.

Because power of about several tens of milliwatts can be supplied to thepower-reception-side circuit, it is possible to arrange an OP AMPcircuit and an AD converter for measuring a voltage and a current and toperform advanced digital processing and processor processing. It is alsopossible to encrypt information to be exchanged and data to be recorded.Also, control of forced discharging of the battery cell and PWMoperation are possible, and display by an LED or liquid crystal ispossible.

When a magnetic field is weak, a circuit configured to shut off theconnection of the battery cell side is provided in thepower-reception-side circuit, so that a malfunction can be preventedeven when unexpected magnetic-field coupling occurs.

Also, in the communication operation and the power-supply operation,because the load resistance connected to the resonance circuit includingthe power reception coil significantly changes, switching is performedon the resonance capacitor. Also, because load resistance is large atthe time of startup, a parallel capacitor is configured to be large inorder to operate the resonance circuit as a parallel resonance circuit.

FIG. 14 is a diagram illustrating a circuit example in which thepower-reception-side circuit has a resonance switching circuit forswitching between a communication operation and a power-supplyoperation.

A resonance switching circuit 83 is connected between a resonancecircuit 81 including a power reception coil RC and a resonance capacitorCa and a rectification circuit 82. The resonance switching circuit 83has a capacitor Cb, a transistor Q1, a transistor Q2, and a resistor Ra.

One end of the capacitor Cb is connected to a line L11 which is one ofconnection lines connecting the resonance circuit 81 and therectification circuit 82. The transistor Q1 is, for example, anN-channel type MOS transistor, a base thereof is grounded, and a drainthereof is connected to the other end of the capacitor Cb. Thetransistor Q2 is, for example, an N channel type MOS transistor, a basethereof is grounded and a drain thereof is connected to a gate of thetransistor Q1. One end of the resistor Ra is connected to the one end ofthe capacitor Cb and the other end thereof is connected to a connectionend of the gate of the transistor Q1 and the drain of the transistor Q2.Also, both or one of the transistors Q1 and Q2 may be an NPN bipolartransistor.

Switching of the resonance capacitor by the resonance switching circuit83 is performed by supplying a resonance switching signal RS from thecontrol circuit 78 to a gate of the transistor Q2.

At the time of startup, the resonance switching signal RS is at an Llevel (a ground level) and the transistor Q2 is turned off. When amagnetic field is applied, charge is supplied through the resistor Ra, agate potential of the transistor Q1 increases, and the transistor Q1 isturned on. Thereby, the capacitor Cb is connected to the resonancecircuit 81 and parallel capacitance increases.

By setting the resonance switching signal RS to an H level, thetransistor Q2 is turned on and the gate potential of the transistor Q1is pulled down to the ground potential, so that the transistor Q1 isturned off. Thereby, the capacitor Cb is disconnected from the resonancecircuit 81, the resonance capacitance decreases, and a state suitablefor power transmission is reached. Also, the resistor Ra may beconnected between the output of the rectification circuit 82 and thegate of the transistor Q1. By applying a magnetic field, charge can besimilarly supplied and each transistor can be turned on.

FIG. 15 is a block diagram illustrating a configuration of a batterymonitoring device 510 which is another configuration example of thebattery monitoring device of the present embodiment. Thepower-transmission-side circuit 61 is connected to power transmissioncoils TC11 and TC12 via the switches SW11 to SW14. The powertransmission coil TC11 is arranged at a position where magnetic-fieldcoupling with the power reception coils RC1 and RC2 is possible. Thepower transmission coil TC12 is arranged at a position wheremagnetic-field coupling with the power reception coils RC3 and RC4 ispossible.

The power-transmission-side circuit 61 controls ON/OFF of the switchesSW11 to SW14 to select either one of the two power transmission coilsTC11 and TC12, transmits a high-frequency signal of 13.56 MHz, andcauses the selected power transmission coil to generate a high-frequencymagnetic field.

When the power transmission coil TC11 is selected, the selected powertransmission coil TC11 has magnetic-field coupling with either one ofthe power reception coils RC1 and RC2. When the power transmission coilTC12 is selected, the selected power transmission coil TC11 ismagnetic-field coupled with either one of the power reception coils RC3and RC4. Thereby, a high-frequency electromotive force is generated byelectromagnetic induction in any one of the power reception coils RC1 toRC4.

According to this configuration, it is possible to reduce the number ofpower transmission coils and the number of wiring lines, as comparedwith the battery monitoring device illustrated in FIG. 10.

Next, an antenna structure (a coil structure) in the battery monitoringdevice 500 illustrated in FIG. 10 will be described with reference toFIGS. 16(a) and 16(b). In the following description, the powertransmission coil is also referred to as a power transmission antenna,and the power reception coil is also referred to as a power receptionantenna.

As illustrated in FIG. 16(a), the power reception antenna is arranged ona side surface of a battery pack BP. The battery pack BP stores batterycells, and has, for example, a rectangular parallelepiped shape. Apower-reception-side circuit configured as an integrated circuit isconnected to each power reception antenna.

The power transmission antenna is configured in a spiral conductorpattern inside a flat isolator medium IM or on a surface thereof in astrip shape, a tape shape, a string shape, a plate shape, and the likeand is connected to a selection switch of the power-transmission-sidecircuit according to a linear conductor pattern. Each power transmissionantenna may be independently connected to the power-transmission-sidecircuit or may be connected to the power-transmission-side circuit in aform branching from the middle.

As illustrated in FIG. 16(b), each power transmission antenna isarranged overlapping the corresponding power reception antenna. Thepower transmission antenna and the power reception antenna are fixed byvarious types of means such as screwing, incorporation into a framestructure, an adhesive tape, and adsorption by a permanent magnet.

According to this configuration, the power reception coil arranged inthe battery pack does not become a protrusion. Although it is desirablethat the periphery of the power reception coil be a nonmagnetic materialor an isolator, an operation is possible even with some magnetism andconductivity.

Also, attachment and detachment are facilitated, and connectionreliability is superior as compared with the case in which electricalcontact points are provided. Also, even if there is a slight air gap,dirt, or wetting between the power transmission coil and the powerreception coil, an operation can be performed.

Also, even if there is an error in a disconnection or a connectioncombination, it is possible to detect an abnormality through IDconfirmation of NFC communication.

Also, because a signal is suitable for an automatic production line andis a high-frequency signal, an operation can be performed regardless ofa direction of a winding direction of the coil.

Next, the antenna structure (the coil structure) in the batterymonitoring device illustrated in FIG. 15 will be described withreference to FIG. 17.

Two power reception coils are provided on adjacent surfaces (forexample, a bottom surface and an upper surface) of two adjacent batterypacks (BP1 and BP2 or BP3 and BP4) and are arranged facing each other.One power transmission coil is arranged to be sandwiched between the twopower reception coils (that is, between the adjacent surfaces of the twobattery packs).

According to this configuration, it is possible to reduce the number ofpower transmission coils and the number of wiring lines withoutincreasing an area and a volume and to implement an inexpensive,compact, and lightweight device.

Also, the configuration of the power transmission coil may be configuredby connecting two power transmission coils TC1 and TC2 in series asillustrated in FIG. 18(a) and configured by connecting the two powertransmission coils TC1 and TC2 in parallel as illustrated in FIG. 18(b).

Also, a capacitor may be connected in series to the power transmissioncoil on a connection line (a signal path) between thepower-transmission-side circuit 61 and each power transmission coil.FIG. 19 is a block diagram illustrating a configuration of a batterymonitoring device 520 having such a configuration.

A capacitor C11 a is connected between one end of the power transmissioncoil TC1 and the switch SW1 and a capacitor C11 b is connected betweenthe other end of the power transmission coil TC1 and the switch SW2. Acapacitor C12 a is connected between one end of the power transmissioncoil TC2 and the switch SW3 and a capacitor C12 b is connected betweenthe other end of the power transmission coil TC2 and the switch SW4. Acapacitor C13 a is connected between one end of the power transmissioncoil TC3 and the switch SW5 and a capacitor C13 b is connected betweenthe other end of the power transmission coil TC3 and the switch SW6. Acapacitor C14 a is connected between one end of the power transmissioncoil TC4 and the switch SW7 and a capacitor C14 b is connected betweenthe other end of the power transmission coil TC4 and the switch SW8.

Also, a capacitor may be connected in series to the power reception coilon a connection line (a signal path) between each power reception coiland the power-reception-side circuit. FIG. 20 is a block diagramillustrating a configuration of a battery monitoring device 530 havingsuch a configuration.

Capacitors C21 a and C21 b are connected between the power receptioncoil RC1 and the power-reception-side circuit 71 a. Capacitors C22 a andC22 b are connected between the power reception coil RC2 and thepower-reception-side circuit 71 b. Capacitors C23 a and C23 b areconnected between the power reception coil RC3 and thepower-reception-side circuit 71 c. Capacitors C24 a and C24 b areconnected between the power reception coil RC4 and thepower-reception-side circuit 71 d.

Although a high-frequency current of 13.56 MHz flows through the powertransmission coil and the power reception coil, an operation can beperformed as in the case in which the capacitors are not connected inseries because the high-frequency current is applied even when thecapacitors are connected in series.

In this manner, by connecting the capacitors in series to the signalpath of the power transmission coil or the power reception coil, a DCcan be blocked. Although the power transmission coil and the powerreception coil are originally isolated, it is possible to prevent fireand electric shock accidents due to electric leakage and shortcircuiting according to a DC element of a capacitor even if isolationbreakdown occurs due to medium damage, moisture intrusion into a crack,or the like.

Embodiment 4

A battery monitoring device of the present embodiment is different fromthe battery monitoring device of the third embodiment in that the powertransmission circuit is duplexed.

FIG. 21 is a block diagram illustrating a configuration of a batterymonitoring device 800 of the present embodiment. The battery monitoringdevice 800 includes a first power transmission circuit 600 a and asecond power transmission circuit 600 b.

The first power transmission circuit 600 a includes apower-transmission-side circuit 61 a and switches SW1 a to SW8 a. Thepower-transmission-side circuit 61 a is connected to one of powertransmission coils TC1 a, TC2 a, TC3 a, and TC4 a in accordance withON/OFF of the switches SW1 a to SW8 a.

The second power transmission circuit 600 b has apower-transmission-side circuit 61 b and switches SW1 b to SW8 b. Thepower-transmission-side circuit 61 b is connected to any one of powertransmission coils TC1 b, TC2 b, TC3 b, and TC4 b in accordance withON/OFF of the switches SW1 b to SW8 b.

FIG. 22 is a diagram illustrating an antenna structure (a coilstructure) of the battery monitoring device 800. The power receptionantenna is arranged on a side surface of a battery pack BP having, forexample, a rectangular parallelepiped shape for storing battery cells,and a power-reception-side circuit configured as an integrated circuitis connected thereto. In both the first power transmission circuit 600 aand the second power transmission circuit 600 b, the power transmissionantenna is configured inside isolator media IM1 and IM2 or on surfacesthereof according to a spiral conductor pattern and is connected to aselection switch of the power-transmission-side circuit according to alinear conductor pattern.

As illustrated in FIG. 23, the power transmission antennas of the firstpower transmission circuit 600 a and the second power transmissioncircuit 600 b are arranged so that a central axis of any coil thereinoverlaps a central axis of the corresponding power reception coil.

Referring again to FIG. 21, in the operation of the battery monitoringdevice 800, control is performed so that one of thepower-transmission-side circuit 61 a of the first power transmissioncircuit 600 a and the power-transmission-side circuit 61 b of the secondpower transmission circuit 600 b is in an operation state (an operationsystem) and the other thereof is in a standby state (a standby system).

For example, when the power-transmission-side circuit 61 a is theoperation system and the power-transmission-side circuit 61 b is thestandby system, the switches SW1 a to SW8 a are controlled so that theyare turned on or off by a host control circuit (not illustrated) and thepower-transmission-side circuit 61 a is connected to any one of thepower transmission coils TC1 a, TC2 a, TC3 a, and TC4 a. Thepower-transmission-side circuit 61 a exchanges information with apower-reception-side circuit (any one of 71 a to 71 d) corresponding tothe power reception coil (any one of RC1 to RC4) coupled to theconnected power transmission coil. At this time, all the switches SW1 bto SW8 b in the second power transmission circuit 600 b are controlledso that they are turned off.

When switching is performed between the operation state and the standbystate, all the switches SW1 a to SW8 a in the first power transmissioncircuit 600 a are turned off. The second power transmission circuit 600b controls ON or OFF of the switches SW1 b to SW8 b so that the powertransmission circuit 61 b is connected to any one of the powertransmission coils TC1 b, TC2 b, TC3 b, and TC4 b. Thereby, thepower-transmission-side circuit 61 b exchanges information with thepower-reception-side circuit (any one of the power-reception-sidecircuits 71 a to 71 d) corresponding to the power reception coil (anyone of RC1 to RC4) coupled to the connected power transmission coil.

According to the battery monitoring device of FIG. 21, because aninformation transmission path is duplexed, it is possible to perform anoperation in the other circuit even if a failure occurs in one circuit.Thereby, a highly reliable device can be implemented.

Also, because all selection switches of the power-transmission-sidecircuit of the standby system are controlled so that they are turnedoff, there is no connection to the power-transmission-side circuit ofthe standby system. Thereby, it is possible to reduce the influence ofthe power-transmission-side circuit of the standby system on thetransmission operation of the power-transmission-side circuit of theoperation system and implement more reliable exchange of information.

Also, because a magnetic-field coupling part is duplexed, interferencebetween the operation system and the standby system is little.

Also, because the power-transmission-side circuit of the operationsystem and the power-transmission-side circuit of the standby system canbe identified according to the ID of the NFC communication or the like,it is possible to reliably detect an abnormality such as a disconnectionor a connection error.

Also, the embodiments of the invention are not limited to theabove-described embodiments. Although an example using a high-frequencymagnetic field of 13.56 MHz has been described, a magnetic field havinga frequency in a different frequency band, for example, such as 100 kHzor 6.78 MHz, may be used, for example, in the above-describedembodiment. Also, an electromagnetic field of several hundred MHz may beused. By designing a power transmission antenna (a power transmissioncoil) and a power reception antenna (a power reception coil) suitablefor each frequency, it is possible to configure a device that performssimilar operations using magnetic fields or electromagnetic fields ofthese frequencies.

Also, the configuration of the signal transmission device and thebattery monitoring device of the embodiments of the invention can beused for high-voltage devices in addition to battery monitoring andpower line monitoring.

Also, a position of a transmission side and a position of a receptionside may be varied, or the power transmission coil and the powerreception coil may be configured to rotate with each other. Also, thepower transmission side and the power reception side may be configuredto be detachable.

Also, the signal transmission device and the battery monitoring deviceof the embodiments of the invention may be operated in an environmentsuch as underwater, in oil, or in cosmic space.

Waterproofing or airtight processing may be applied to the powertransmission coil and the power reception coil. Also, a magnetic sheetmay be used to magnetically shield the power transmission coil and thepower reception coil from the outside. Also, a filter for suppressingharmonics may be used.

Also, an example of a battery monitoring device configured to monitorfour battery cells has been described in the above-described Embodiments3 and 4. However, the number of battery cells is not limited thereto andthe battery monitoring device is configured as a battery monitoringdevice that monitors n (n is an integer greater than or equal to 2)battery cells, wherein the number of power transmission coils, thenumber of power reception coils, and the number of power-reception-sidecircuits are set as n.

What is claimed is:
 1. A signal transmission device connected to anoperation device including an operation circuit configured to perform anoperation based on a first voltage from a power supply, a measurementcircuit configured to obtain measurement data by measuring an electricalsignal using the first voltage as a reference, and a process controlcircuit configured to operate based on a second voltage obtained byconverting the first voltage into a voltage with a voltage level lessthan the first voltage and control an operation of the operation circuitbased on the measurement data and configured to transmit and receive asignal between the process control circuit and the measurement circuit,the signal transmission device comprising: a power transmission circuithaving a power-transmission-side resonance circuit including a powertransmission coil and a power-transmission-side resonance capacitor andconfigured to wirelessly perform transmission of power and transmissionand reception of information according to an alternating current (AC)magnetic field from the power transmission coil; and a power receptioncircuit having a power-reception-side resonance circuit including apower reception coil and a power-reception-side resonance capacitor andconfigured to wirelessly perform reception of power and transmission andreception of information via the power reception coil according to theAC magnetic field, wherein the power reception circuit supplies thepower from the power transmission circuit to the measurement circuit andacquires the measurement data from the measurement circuit to transmitthe acquired measurement data to the power transmission circuit, andwherein the power transmission circuit transmits the power from theprocess control circuit to the power reception circuit and receives themeasurement data from the power reception circuit to supply the receivedmeasurement data to the process control circuit.
 2. The signaltransmission device according to claim 1, wherein the power transmissioncircuit comprises: a driving circuit configured to supply a drivingcurrent to the power transmission coil to generate the AC magneticfield; and a driving control circuit configured to control the drivingcircuit, wherein the power reception circuit comprises a load switchingcircuit configured to perform switching of a state of a load connectedto the power-reception-side resonance circuit in accordance with a loadswitching signal, wherein the driving circuit comprises a currentmeasurement circuit configured to measure the driving current, andwherein the driving control circuit detects a change in the state of theload in the power reception circuit based on a change in the drivingcurrent measured by the current measurement circuit.
 3. The signaltransmission device according to claim 1, wherein the power transmissioncoil includes: a wiring part arranged on a first wiring layer in asubstrate having a plurality of wiring layers and including a continuousconductor wire having one end connected to the power-transmission-sideresonance capacitor; a spiral part having first and second ends and aconductor wire part, wherein the first end is connected to thepower-transmission-side resonance capacitor and the conductor wire partincludes a spiral continuous conductor wire arranged on the first wiringlayer and crosses a space between the second end and the other end ofthe wiring part; and a connection part including a continuous conductorwire part arranged on a second wiring layer of the substrate andconfigured to connect the second end of the spiral part and the otherend of the wiring part via a pair of vias provided between the firstwiring layer and the second wiring layer, wherein the power receptioncoil comprises: a wiring part arranged on the second wiring layer andincluding a continuous conductor wire having one end connected to thepower-reception-side resonance capacitor; a spiral part having first andsecond ends and a conductor wire part, wherein the first end isconnected to the power-reception-side resonance capacitor and theconductor wire part comprises a spiral continuous conductor wirearranged on the second wiring layer and crosses a space between thesecond end and the other end of the wiring part; and a connection partincluding a continuous conductor wire part arranged on the first wiringlayer and configured to connect the second end of the spiral part andthe other end of the wiring part via a pair of vias provided between thefirst wiring layer and the second wiring layer.
 4. The signaltransmission device according to claim 3, wherein the conductor wirepart of the connection part of the power transmission coil is arrangedseparated from the spiral part and the wiring part of the powerreception coil on the second wiring layer, and wherein the conductorwire part of the connection part of the power reception coil is arrangedseparated from the spiral part and the wiring part of the powertransmission coil on the first wiring layer.
 5. The signal transmissiondevice according to claim 4, wherein the conductor wire part of theconnection part of the power transmission coil is arranged inside thespiral part of the power reception coil on the second wiring layer, andwherein the conductor wire part of the connection part of the powerreception coil is arranged inside the spiral part of the powertransmission coil on the first wiring layer.
 6. The signal transmissiondevice according to claim 4, wherein the conductor wire part of theconnection part of the power transmission coil is arranged outside ofthe spiral part of the power reception coil on the second wiring layer,and wherein the conductor wire part of the connection part of the powerreception coil is arranged outside of the spiral part of the powertransmission coil on the first wiring layer.
 7. A battery monitoringdevice for monitoring states of n battery cells, wherein n is an integergreater than or equal to 2 and the battery monitoring device comprises:a power transmission circuit having m power transmission coils andconfigured to cause any one of the m power transmission coils togenerate an AC magnetic field and wirelessly perform transmission ofpower and transmission and reception of information, wherein m is aninteger less than or equal to n; n power reception circuits provided incorrespondence with the n battery cells and the m power transmissioncoils, each of the n power reception circuits having a power receptioncoil and wirelessly performing reception of power and transmission andreception of information via the power reception coil; and n measurementcircuits provided in correspondence with the n power reception circuitsand the n battery cells and configured to receive power supplied fromthe n power reception circuits and measure voltage values of the nbattery cells, wherein the power transmission circuit selects any one ofthe m power transmission coils in accordance with a battery cell of amonitoring target among the n battery cells, causes the selected powertransmission coil to generate the AC magnetic field, and receives ameasurement result of a voltage value of the battery cell of themonitoring target.
 8. The battery monitoring device according to claim7, wherein each of the n power reception circuits comprises: adischarging unit configured to discharge a corresponding battery cellamong the n battery cells; and a power supply unit configured to supplythe power transmitted from the power transmission circuit to thecorresponding battery cell of the n battery cells.
 9. The batterymonitoring device according to claim 8, wherein each of the n powerreception circuits further comprises a resonance switching circuitconfigured to switch capacitance of the power reception circuit at atime of communication operation and at a time of power-supply operation,and wherein the resonance switching circuit connects a resonancecapacitor having a predetermined capacitance to the power reception coilat the time of communication operation, and wherein the resonanceswitching circuit disconnects the resonance capacitor and the powerreception coil at the time of power-supply operation.
 10. The batterymonitoring device according to claim 7, wherein the power transmissioncircuit has a capacitor configured to conduct an AC signal and block adirect current (DC) in a signal path of the m power transmission coils.11. The battery monitoring device according to claim 7, wherein each ofthe n power reception circuits has a capacitor configured to conduct anAC signal and block a DC in a signal path of the power reception coil.12. The battery monitoring device according to claim 7, wherein thepower transmission circuit has a first power transmission circuit and asecond power transmission circuit each having m power transmission coilsand configured to cause one of the m power transmission coils togenerate an AC magnetic field and wirelessly perform transmission ofpower and transmission and reception of information; and wherein, inaccordance with an input of a setting signal, one of the first powertransmission circuit and the second power transmission circuit is set asan operation system circuit to execute the transmission of the power andthe transmission and reception of the information and the other is setas a standby system circuit to stop an operation.
 13. The batterymonitoring device according to claim 7, wherein each of the n batterycells are stored in any one of n battery packs, wherein the powerreception coil of each of the n power reception circuits is provided onany one surface of the battery pack of a corresponding battery cell, andwherein each of the m power transmission coils is formed as a conductorpattern on a medium with a flat shape and is arranged at a positioncapable of magnetic field coupling with the corresponding powerreception coil.
 14. The battery monitoring device according to claim 13,wherein each of the power reception coils is provided on an adjacentsurface of an adjacent battery pack among the n battery packs, andwherein the power transmission coil is arranged between a pair of powerreception coils provided on the adjacent surface.
 15. A batterymonitoring method for use in the battery monitoring device according toclaim 8, the battery monitoring method comprising the steps of:sequentially selecting, by the power transmission circuit, each of the nbattery cells as a battery cell of a monitoring target, selecting acorresponding power transmission coil among the m power transmissioncoils, and causing the power transmission coil to generate the ACmagnetic field; receiving a measurement result of a voltage value of thebattery cell of the monitoring target from the power reception circuit;calculating an average value of the measurement results of the n batterycells; comparing a number of high-voltage cells having a voltage whichis a predetermined allowable value greater than the average value amongthe n battery cells with a number of low-voltage cells having a lowvoltage which is the predetermined allowable value less than the averagevalue; and discharging the high-voltage cells if the number ofhigh-voltage cells is greater than the number of low-voltage cells andcharging the low-voltage cells if the number of low-voltage cells isgreater than the number of high-voltage cells.